Obstructive Sleep Apnea (OSA) and other dangerous sleep-disordered breathing (SDB) conditions affect thousands worldwide. Numerous techniques have emerged for the treating SDB, including, for example, the use of Continuous Positive Airway Pressure (CPAP) devices, which continuously provide pressurized air or other breathable gas to the entrance of a patient's airways via a patient interface (e.g. a mask) at a pressure elevated above atmospheric pressure, typically in the range 3-20 cm H2O. Typically, patients suspected of suffering from SDB register with a certified sleep laboratory where sleep technicians fit patients with numerous data collectors and monitor their sleep activity over a given period. After the patient is diagnosed, a treatment regimen usually is developed, identifying both a treatment apparatus (or treatment apparatuses) and program of use for the treatment apparatus(es).
FIG. 1 shows a simplified schematic of a typical CPAP treatment apparatus. An impeller 1 is powered by an electric motor 2 using a servo 3 under the direction of a microprocessor-based controller 4. The supply of breathable gas is carried to the mask 5 through a flexible conduit 6. The apparatus has various switches 7, displays 8, and a number of transducers. The transducers may monitor a number of processes, such as, for example volumetric flow rate 10 (e.g., at a predetermined point in the flow path), pressure 11 (e.g., at a predetermined point downstream of the flow generator outlet or at the mask), snore 12, flow generator rotational speed 13, and/or motor parameters 14.
It would be advantageous to detect faults in the treatment apparatus as they develop during the operation of the blower. A gross failure of a motor bearing and/or turbine results in the patient ceasing to receive treatment. However, if a motor bearing and/or turbine begin(s) to fail, a patient may receive sub-optimal treatment for the period of time between the beginning of the failure and when the failure is complete. A failing motor may result in low (or lower than expected) pneumatic output. Failing to recognize developing faults also may cause the bearing to overheat, which may, in turn, result in a potential hazards.
To this end, U.S. Pat. No. 5,621,159, the entire contents of which is incorporated herein by reference, discloses techniques for determining increased rotational friction. Unfortunately, further improvements to these techniques are necessary, as they require powering down the fan for a predetermined period to check the spin-down rate, which makes such techniques inappropriate for flow generators actually in use.
Certain other techniques for detecting faults are described in AU 764761, and U.S. Pat. Nos. 6,591,834, 6,745,768, and 7,040,317, the entire contents of each of which is hereby incorporated herein by reference. Further improvements to these techniques also would be advantageous, as there are certain faults that cannot be detected using such techniques. For example, such techniques generally cannot determine whether there is a faulty bearing that is not yet causing a “motor stalled” condition or a near-motor-stalled condition. It would be advantageous to detect other failures, such as, for example, low output torque, increased bearing friction, constricted inlet(s), faulty or disconnected Hall sensor(s), etc.
Thus, it will be appreciated that there is a need in the art for improved motor fault detection techniques.